Ferromagnetic ore concentrator and method of processing ores therewith

ABSTRACT

A ferromagnetic ore concentrator having an inclined, adjustable nonmagnetic plate, at the top portion and on one side of which is supplied particulate material, including ferromagnetic particles. One or more magnetic core structures are positioned on the other side of the plate to create a varying magnetic field in which the lines of force are predominantly in the direction of the normal downward movement of the particles past the plate. The magnetic field cyclically varies to and from substantially zero intensity, and is predominantly of a single polarity. Separated material is collected below the plate. A magnetic circuit is utilized, characterized by a magnetic core having a &#39;&#39;&#39;&#39;lossy&#39;&#39;&#39;&#39; hysteresis loop. Primary and secondary coils are wound on the core and are magnetically coupled together, the primary coil being energized by alternating current and the secondary coil being included in a circuit which limits the flow of current substantially to a single direction, such as by a diode shorting the secondary coil.

United States Patent 72] Inventors John Ernest Burgener Clarkson, Ontario; Peter Mladenovich, Scarborough, Ontario, Canada [21 Appl. No. 633,473

[22] Filed Apr. 25, 1967 [45] Patented Jan. 5, 197] [731 Assignee Burgener Technical Enterprises Limited Ontario, Canada a Canadian corporation [54] FERROMAGNETIC ORE CONCENTRATOR AND METHOD OF PROCESSING ORES THEREWITH 24 Claims, 19 Drawing Figs.

[52] [1.5. CI 209/214, 209/223, 209/227 [51] Int. Cl B03c 1/08, 1303c 1/24 [50] Field of Search 209/214,

[ 56] References Cited UNITED STATES PATENTS 248,115 10/1881 Steams 335/268X 1,425,235 8/1922 Bradley 209/223 1,360,601 11/1920 Ullrich 209/214 3,279,602 10/1966 Kottenstette 209/214 3,368,141 2/1968 Subieta-Garron 335/246 1,564,731 12/1925 Weatherby 209/214 2,975,897 3/1961 Presgrave. 209/214 1,573,094 2/1926 Saal 335/231 arns-:4."

Primary Examiner-Frank W. Lutter Assistant Examiner-Robert Halper Attorneys-Robert S. Dunham, R. J. Dearbom, P. E.

Henniger, Lester W. Clark, John A. Harvey, Gerald W. Griffin, Thomas F. Moran, Howard .1. Churchill and Robert Scobey ABSTRACT: A ferromagnetic ore concentrator having an inclined, adjustable nonmagnetic plate, at the top portion and on one side of which is supplied particulate material, including ferromagnetic particles. One or more magnetic core structures are positioned on the other side of the plate to create a varying magnetic field in which the lines of force are predominantly in the direction of the normal downward movement of the particles past the plate. The magnetic field cyclically varies to and from substantially zero intensity, and is predominantly of a single polarity. Separated material is collected below the plate.

A magnetic circuit is utilized, characterized by a magnetic core having a lossy hysteresis loop. Primary and secondary coils are wound on the core and are magnetically coupled together, the primary coil being energized by alternating current and the secondary coil being included in a circuit which limits the flow of current substantially to a single direction, such as by a diode shorting the secondary coil.

MlDDLlNGS CONCENTRATE PATENTEU JAN 51971 SHEET 1 UF 5 H W NE W A fiE M m 06% R N TR m w w E w A R NE in m w A. y M Y U. 2 DD w z ORE CONCENTRATION ZONE AILINGS I PATENTED JAN 5 WI SHEET 2 OF 5 INVENTORS JOHN BURGENER B PETER MLADENOVCH ATTO RN Ei' ATENTED JAN 5 WI SHEET 3 BF 5 auto/V042) 00/1. 0/?

CO/LS INVENTOR5 JOHN E..BURGEMEK PETER MLADEMOVICH A222 41/. M

ATTO ENE? PATENTEDJAN 5|97l SHEET t [1F 5 A TTO an E) FERROMAGNETIC ORE CONCENTRATOR AND METHOD OF PROCESSING ORES THEREWI'Ill-I SUMMARY OF THE INVENTION This invention relates to the concentration of ore, and particularly to the concentration by separation of mixtures of particles including ferromagnetic material.

Ferromagnetic ore concentrators have been employed in the past to separate particles of ferromagnetic material from particles of nonferromagnetic material. Such concentrators have typically fed a stream of particles to be separated into a concentration zone wherein the ferromagnetic particles are subject to an oscillating field force and both ferromagnetic and nonferromagnetic particles are subject to another force, for example, gravity. The resultant of the two forces acting on the ferromagnetic particles directs such particles along a different path than the nonferromagnetic particles, the latter being subject only to a gravitational force, for example, and in this fashion the separation is completed. It has been common practice to employ a sinusoidally varying magnetic field which oscillates between opposing polarities of equal magnitude.

It has been found in the present invention that the separation of ferromagnetic from nonferromagnetic particles may be greatly enhanced through the use of a magnetic field which varies to an from substantially zero intensity and which is of a single polarity for the major portion of each cycle. The polarity may change, but the change is of relatively short duration. In other words, a magnetic field is provided in one direction for a relatively long period during each cycle, and then is reduced roughly to zero, e.g., reversed for a short period of time. Thus, ferromagnetic particles are attracted by the magnetic field for a relatively long time in each cycle, following which the field is efiectively removed to permit the particles to move in another direction under gravitational action. The action of the magnetic field on the ferromagnetic particles causes such particles to travel in a path differently from that of the nonferromagnetic particles, and in this fashion the ferromagnetic and nonferromagnetic particles are separated from each other.

It has also been found in the present invention that particles of ferromagnetic material may be grouped according to degree of ferromagnetism by changing the magnetic field at one or more locations in the concentrating zone. For example, if the magnetic field at a particular location is reduced somewhat, relatively weak ferromagnetic particles which were previously just held against falling out of the field will be permitted to fall out of the field while stronger ferromagnetic particles will still be maintained within the field. In this fashion the weak and strong ferromagnetic particles may be separated from each other.

Accordingly, an object of the present invention is to provide improved ore concentration.

Another object of the invention is to provide improved ferromagnetic ore concentration utilizing a cyclically varying magnetic field in which the field varies to and from substantially zero intensity and is of a single polarity for the major portion of each cycle.

In illustrative embodiments of the present invention, a cyclically varying magnetic field is created through the use of an alternating field superimposed on a constant field, or by a transformer action in which a primary coil is energized by an alternating current supply and a secondary coil provides a unidirectional field by a diode in the circuit thereof to limit the current through the secondary coil substantially to a single direction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of representative ore concentration apparatus in accordance with the invention.

FIG. 2 is a sectional view of the apparatus shown in FIG. 1 taken along the section line 2-2.

FIGS. 3a and 3b are waveforms showing magnetizing force as a function of time, FIG. 30 is a hysteresis curve and FIG. 3d

is a waveform showing the variation of magnetic field with time, all of which are useful in understanding the magnetic principles involved in the invention.

FIGS. 4 and 5 show representative core and coil structures which may be used to produce an electromagnetic field useful in practicing the invention.

FIG. 6 is a schematic circuit diagram of a circuit useful in practicing the invention.

FIG. 7a shows a representative core and coil arrangement which may be employed in a circuit such as shown in FIG. 6.

FIG. 7b is a schematic circuit diagram of a plural coil arrangement. connected in a circuit as shown in FIG. 6.

FIGS. 8a and 8b are waveforms showing magnetizing force as a function of time. FIG. is a hysteresis curve and FIG. 8d is a waveform showing the variation of magnetic field with time, all of which are useful in understanding the operation of the circuit of FIG. 6.

FIGS. 9 and 10 show further representative magnetic core and coil structures which may be used to produce an electromagnetic field useful in practicing the invention.

FIGS. Ila and 11b are polarity diagrams showing the magnetic fields in connection with the apparatus of FIG. 1.

Referring to FIG. 1, particulate ore to be concentrated, including ferromagnetic particles, is applied to a hopper 15 from which it passes through an outlet 15a. The hopper outlet 15a is formed in part by a plate 16 which may be of any nonmagnetic material, such as wood, aluminum or brass. The plate 16 is inclined beneath the hopper outlet 15a and defines the upper boundary of an ore concentration zone 17. The plate 16 is attached at its upper end to a strap 16a. A plurality of magnetic core structures 18 are positioned over the plate 16 on the side of the plate opposite from the concentration zone. Four such core structures, 18a, 18b, 18c and 18d are shown. The number of such core structures is arbitrary, and in some cases a single core structure will suffice. The core structures include corresponding coil assemblies 20 wound thereon. For example, the coil assembly 29a is wound upon the core structure 18a. The core structures are retained in place by associated mounting members 22; for example the core structure 13a is mounted by associated mounting member 2211.

The core structures also serve to retain the plate 16 thereagainst. As shown in FIG. 2 in connection with the core structure 18a, clamps 24a and 24b are attached to the core structure and include U-sliaped portions 24a and 24b which engage the edges of the plate 16 to retain the plate in position against core structure. The strap 16a shown in FIG. I attached to the upper end of the plate 16 and the mounting members 22 may be adjusted (as shown by the double headed arrows adjacent thereto) so that the positions of the core structures and the upper end of the plate 16 can be changed. In this fashion, the inclination of the plate 17 defining the upper boundary of the concentration zone 17 can be changed at various positions throughout the zone. For certain materials to be concentrated, it may be desirable to incline the plate more steeply than for other materials.

The plate 16 is shown in FIG. 2 as being retained by the U- shaped portion of clamps 24a and 24b against the core structure 18b. The touching of the core structures by the plate is not necessary. It may be desirable to mount the plate independently of the core structures and to provide for a change in the positions of the core structures relative to the plate (e.g. in a direction perpendicular to the plate) to provide an adjustment of the field. The positions of the core structures may also be made to vary parallel to the plate to provide a further adjustment of the field. Also it should be noted that the inclination of the plate need not be changed uniformly, that is, portions of the plate may be inclined more steeply than other plate portions in order to provide a bellying of the plate to enhance the concentration of ore by changing the field.

The magnetic fields produced by the core structures 18 beneath the plate t6 cyclically vary with respect to time so that each is of a single polarity during the major portion of each cycle of variation and is reduced substantially to zero in- .away from the plate for a relatively short time under the force of gravity. Additionally, as the magnetic field reverses, at least some of the ferromagnetic particles may .be repulsed or rotated by the field since the aligned dipoles constituted by the particles may not immediately change polarity because of hysteresis of the particles. It has been found,v however, that most ferromagnetic particles will be. immediately polarized once they encounter the magnetic fields beneath the plate 16 and will retain the same polarization.

In the case of plural magnetic core assemblies as shown in FIG. 1, it is desirable to alternate the polarities of the windings .20 on the core assemblies so that as the particles move down the plate 16 and pass by succeeding core assemblies, the fields change. For example, the field opposite the center of core 18a may provide a North pole for the major portion of each cycle of variation, while the field opposite the center of core 18b may provide a South pole for the major portion of each cycle of variation. The polarized particles of ferromagnetic material are thus rotated many times under the plate 16 as they move along the plate past succeeding core assemblies. In particular, the particles rotate 180 as they pass'from the center of one core to another. Thus in the four core assembly arrangement shown in FIG. 1 the particles of concentrate rotate a full 360 as they pass from the core assembly 18a to. the core assembly 180 and then rotate another 180 as they pass from opposite the core amembly 18 c to the core assembly 18d.

The varying fields beneath each core assembly oscillate the ferromagnetic particles and the succeeding changes in the fields from one assembly to another rotate the particles so that the ferromagnetic and nonferromagnetic particles are shaken apart or separated from each other.

A hopper 30 may be positioned beneath the plate 16 and divided into compartments 30a, 30b and 300 so as to accumulate the particles dropping from beneath the plate 16. In particular, the compartment 30c positioned directly below the upper end of the plate 16 may receive the tailings of the ore, which comprise nonferromagnetic or weakly ferromagnetic material. The compartment 30b positioned underneath the midportion of the plate 16 may receive the middlings, which are particles formed of some ferromagnetic material and some nonferromagnetic material, or of relatively weak ferromagnetic material of stronger ferromagnetism than that of the material comprising the tailings. The compartment 30a positioned beneath the lower-portion of the plate 16 may receive the concentrate of the ore, which is formed of particles composed of almost entirely ferromagnetic or very strong ferromagnetic material. It will be appreciated that the higher the ferromagnetic content in a particle the longer will the particle be retained in the vicinity of the plate 16 during its movement along the plate.

As will be noted from FIG. 1, the plate 16 is curved or bellied at different portions thereof. It will be further noted that the spacing of the core structures 18 from each other varies at the plate 16 so that proceeding downwardly from the plate the core structures are spaced greater distances apart. As noted above, the core structures also may be spaced different distances from the plate. In this fashion the magnetic field is changed at different positions in the concentration zone 17. The changing of the magnetic field permits particles of ferromagnetic material of varying degrees of ferromagnctism to be separated from each other. In particular, since each particle of material underneath the plate 16 is subjected to an unchanging gravitational force, a change in the magnetic force, either in its direction (by changing the inclination of plate 16) or intensity (by changing the spacing of the magnets from each other or from the plate), is necessary to separate particles of material according to their degree of ferromagnetism. For example,.if a weakly ferromagnetic particle is just carried along the plate 16 above the compartment 300, the

. change in direction of the plate over the compartment 30b and the increased spacing of the core assemblies 18b and i180 in this region of the plate will change the magnetic forces acting on the particle so that the'net force (gravitational and magromagnetic particles .will still be such as to retain the particles against the plate where they will be carried down the plate past the compartment 30b and over the compartment 300. At this point the plate curvature changes and the field becomes relatively weak, permitting the strongly ferromagnetic particles to fall within compartment 30a. An example of the separation of particles of different degrees of ferromagnetism is the separation of magnetite from ilmenite.

FlGS..3a-3d are helpful in understanding the magnetic principles involved in the invention. In FIG. 3a the dashed curves 32 and 34 show two waveforms of magnetizing force plotted as a function of time. The waveforms represent the magnetizing forces in any one of the coil assemblies 20 shown in the apparatus of FIG. 1, for example. As will be noted, a magnetizing force of constant magnitude, represented by the curve 32, and an alternating magnetizing force varying between positive and negative magnitudes, represented by the curve 34, are produced by each one of the coil assemblies. The manner in which the constant and alternating magnetizing forces are produced will be explained in more detail below. The constant and alternating magnetizing forces combine as shown in curve 36 (FIG. 3b) to provide a net magnetizing force which varies with time. Each ordinate on curve 36 is the sum of the corresponding ordinates in curves 32 and 34. It will be noted that the curve 36 is not symmetrical about the zero axis.

The curve 36, taken with hysteresis curve 38 (FIG. 3c) of the metal forming the core structures 18, provides an indication of the magnetic field produced in each of the core structures by the corresponding coil assembly. In particular, in FIG. 3b the magnetizing force at four different times t,, t t and t may be projected on the curve 38 of FIG. 30. The intersections so located may be projected upwardly to produce curve 40 (FIG. 3d), which is a representation of the resultant magnetic field. With the variation of magnetizing force shown in FIG. 3b, the magnetic core structures 18 of FIG. I traverse the path 38a, 38b shown in FIG. 30. It will be noted that the positive magnetizing force of the curve 36 at the time t, corresponds to point t, on the hysteresis curve of FIG. 3c. This is projected onto FIG. 3d as the point 40a at time t,. As the magnetizing force drops to zero between times t and t (FIG. 3b), the magnetic core structures 18 proceed along the portion 38a of the hysteresiscurve of FIG. 3c, arriving at the point t at the time t;,. The point t in FIG. 3c is projected onto FIG. 3d as point 40b at the time t In this fashion the curve 40 of FIG. 3d is developed from FIGS. 3b and 30.

It will be noted from FIG. 3d that the magnetic field produced by any of the coils 18 varies from a peak valueof one polarity (40a) to a peak value of opposing polarity (400). The net magnetic field provided by each coil assembly is of a single polarity for the major portion of each cycle of magnetic field variation and is reduced to substantially zero intensity. The shaded area designated 42a is the magnetic field present during the major portion of each cycle of variation. The shaded area 42b represents the field of opposing polarity present during the minor portion of each cycle of field variation. The portion. 42b represents a minor reverse field'which persists for a relative short period of time, and the portion 420 represents a significant field which persists for a relative long period of time. The integral overtime of the curve 40 corresponding to the portion 420 is much greater than the integral corresponding to the portion 4211. By this action a cycli cally varying field is produced in the ore concentrating struc' ture ofFIG. 1.

It should be noted that it is desirable to maintain the amplitude of the portion 42b of reverse field shown in FIG. 3d at a relatively small value so that, after remanent magnetism of the core structures 18 shown in FIG. 1 has been avoided, saturation of the field in the other polarity is also avoided. The slight reversal of field polarity indicates that remanent magnetism has been avoided and that the field has been reduced so as to permit the ferromagnetic particles to fall by gravitational force as described above. It will be noted from FIGS. 3b and 30 that by merely dropping the net magnetizing force to zero, such as at the time t a significant remanent magnetism represented by the point 40b in FIG. 3d will result. It is recognized that it may be difficult to provide an operation on a hysteresis curve such that the magnetizing force reduces the resultant field to zero and no more. Hence, as a practical matter it may be necessary to provide some reversal of field in order to be sure that substantial remanent magnetism has been avoided. Furthermore, this field reversal for a short but finite period of time may be effective to cause repulsion and/or rotation of particles which follow a different hysteresis loop than that followed by the core structures. The reversal may therefore assist in vibrating the stream of particles and thus aid in the separation of ferromagnetic from nonferrornagnetic particles.

The hysteresis loop shown in FIG. 30 is such that the transition of flux density from saturation in one direction to saturation in the other direction takes place over a substantial range of magnetizing force I-I. Such a hysteresis curve is characteristic of so-called lossy material, e.g., material having a substantial air gap. With such a material it is relatively easy to achieve operation at or near the point of zero flux density, since slight variations in magnetizing force do not produce significant changes in magnetic field. On the other hand, with socalled low loss materials in which the transition of flux density from saturation in one direction to saturation in the other direction takes place over a relatively small range of magnetizing force H, operation at or near zero flux density is almost impossible to achieve, since any slight variation of magnetizing force results in a substantial change in flux density. As apractical matter, then, it is advantageous to operate with so-called lossy materials.

As noted above, the varying field shown in FIG. 3d is produced by the superimposing of two magnetizing forces as shown in FIG. 3a, namely, a constant magnetizing force and an alternating magnetizing force. FIG. 4 shows a simple magnetic core and coil assembly which produces and superimposes such magnetizing forces. A permanent magnet 44 having two legs 44a and 44b is employed. Coils 46a and 46b are respectively wound about the legs 44a and 44b and are energized by an alternating current source to produce an alternating magnetizing force such as shown by curve 34 (FIG. 3a). The permanent magnet 44 provides a constant magnetizing force such as shown by the curve 32 in FIG. 3a. The AC coils 46a and 46b and the permanent magnet together produce an alternating magnetizing force such as shown by curve 36 in FIG. 3b.

It will be noted that this type of arrangement does not employ an E-shaped core as shown in FIG. 2. The E-shaped core arrangement, which is not essential in practicing the invention, will be explained below.

FIG. 5 shows an arrangement similar to that of FIG. 4, not involving a permanent magnet core, however. Core structure 48 includes two legs 48a and 48b upon which are respectively wound AC coils 50a and 50b as in the arrangement of FIG. 4. A coil 52 is wound about bridging member 480 of the core structure which joins the two legs 48a and 48b. The coil 52 may be energized by a direct current source, so as to provide a constant magentizing force such as shown by curve 32 in FIG. 30.

Alternatively, the coil 52 may be included in a circuit such as that shown in FIG. 6. In FIG. 6 such a coil constitutes the secondary winding of a transformer of which the primary winding is constituted by a primary coil or coils, e.g., the coils 50a and 50b of FIG. 5. The coils 50a and 50b, as was indicated in connection with FIG. 5, are energized by an alternating current supply. The coil 52 of FIG. 5, constituting the secondary winding in FIG. 6, would be connected in the circuit of FIG. 6 in series with a variable resistor 54 and a diode 56. The diode 56 limits the flow of current through the secondary winding substantially to a single direction. That is, the diode 56 presents a relatively low impedance to current flow in one direction and a relatively high impedance to current flow in the other direction. The variable resistor 54 affects the magnitude of current flow in the secondary circuit when the diode 56 is conductive.

The circuit of FIG. 6 is also intended for use with a magnetic core and coil arrangement as shown in FIGS. I and 2, specifically employing an E-shaped core structure in which the coil assembly is wound about the middle leg. FIG. 7a shows such a core and coil assembly in more detail. The E-shaped magnetic core 18 is as shown in FIG. 2. Further, it will be noted that the coil 20 wrapped about the middle leg of the core includes two coils 20-1 and 202. The coil 20-1 constitutes a primary transformer winding such as shown in the circuit of FIG. 6, while the coil 20-2 (wound over the coil 20-!) constitutes a secondary transformer winding as shown in FIG. 6. When plural E-shaped core and coil assemblies as shown in FIGS. l and 2 are employed in a circuit arrangement as shown in FIG. 6, with each core and coil assembly constituting a transformer, the primary and secondary windings should be connected as shown in FIG. 7b. In particular, all the primary windings 20al through 10d1 are connected in series and are energized by any suitable AC supply. The secondary windings 2011-2 through 20d-2 are also connected in series. The secondary circuit is completed by a diode 56 such as that shown in FIG. 6. It will be noted that the primary windings are reversed in polarity for succeeding windings; the same is true with respect to the secondary windings. The reason for this reversal of polarity is to provide for succeedingly different fields throughout the cone concentration zone I7 as noted above and as will be explained in more detail below. FIGS. 8a-8d are similar to FIGS. Fur-3d and the AC involved in a circuit employing primary and secondary transformer windings, with current flow in the secondary limited to a single direction. FIGS. shows the magnetizing with respect to time in the primary and secondary windings of the circuit of FIG. 6. Curve 58 is related to the current flow through the primary winding and curve 60 is related to the current flow through the secon dary winding. The magnetizing forces (ampere-turns) produced by these current flows through their respective windings may be summed to produce a net magnetizing force such as shown by curve 62 in FIG. 8b. The curve 62 is not sinusoidal and is not symmetrical about the zero axis. It will be noted that the peak magnitude of the shaded portion 62a of the curve below the zero axis is less than the peak magnitude of the shaded portion 62b of the curve above the zero axis. Such a magnetizing force will produce a magnetic field as shown in FIG. 8a' (projected from curve 8c in the same manner as explained above in connection with FIGS. Zia-3d) to provide a field of one polarity for the major portion of each cycle of variation and a relatively small field of opposing polarity for a minor portion of each cycle. Such a varying field oscillates the ferromagnetic particles as described above.

FIGS. 9 and I0 are representative core and coil structures differing from the core and coil structures shown in FIGS. 5 and 7a, but also suitable for use in ore concentrators wherein the varying magnetic field is to be produced by transformer action, as just described. In FIG. 9, core structure 66 includes two legs 66a and 6612, with the primary and secondary coils being wound about the leg 66b. In FIG. 10, the arrangement is the same as that in FIG. 9, except that primary and secondary coils are included about both legs 66a and 66b.

As is noted above in connection with FIG.7b, the primary and secondary windings of the plural E-shaped core and coil assemblies are wound so that succeeding windings are reversed with respect to polarity in the series circuit in which they are connected. The purpose of the reversal is to provide a above. Hence, FIG. 11a shows the effective fields in the concentration zone 17 over time.

In each E-shaped core and coil assembly the magnetic lines of force extend either away from the center pole toward the two outerpoles, as shown in FIG. 11a for the assembly 180, or they extend into the center pole from the two outer poles, as shown for the assembly 18b. The field about the center pole of each of the core structures thus is twice as great as the field about each of the outer poles, and hence it has been found in the use of E-shaped cores that the particles of ferromagnetic material tend to move toward the center poles of the cores. Hence, for practical purposes, the width of the ore concentrating zone 17 (designated 70 in FIG. Ila) is limited to the width of the center poles. In apparatus that has been constructed corresponding to that shown in FIG. I, the funnel was shaped so as to apply the material for concentration to an area adjacent to the center pole of the uppermost core assembly 180.-

Because of the change in polarity from one center pole to another, there are magnetic lines of force (as shown by the dashed lines in FIG. 11a) which extend between adjacent poles in the direction of material movement through the concentration zone. These lines of force act upon the ferromagnetic particles travelling through the concentration zone and prevent such particles from falling out of the zone. If adjacent center poles were of the same polarity, however, there would be nomagnetic lines of force extending between center poles in the direction of particle movement through the ore concentration zone. Hence in the areas between adjacent core and coil assemblies, the magnetic field might be insufficient to maintain the ferromagnetic particles within the concentration zone, and the particles might fall out of the concentration zone without passing by all the core and coil assemblies.

In addition, the polarity reversal for succeeding center poles ensures that the particles of ferromagnetic material (which are dipoles) are rotated as they pass by the poles, as described above. The rotation assists in the concentration, since the rotating particles tend to shake the material and to separate the particles from each other.

FIG. 11b shows the arrangement which would be followed if U-shaped cores are employed. The coils have not been shown for simplicity of illustration. The coils are wound and energized so that at any instant of time adjacent poles are of opposite polarity. In this fashion the magnetic lines of force are as shown by the dashed lines in FIG. lib and extend in the direction of particle movement through the concentration zone. The bridging of adjacent poles of different cores by magnetic lines of force avoids dead spots between cores as noted above to maintain the ferromagnetic particles Within the concentration zone. It should be noted that the coils of such U- shaped cores need not be reversed in polarity in a common circuit if connected as shown in FIG. 7b, since the magnetic fields produced by the coils will produce the succeedingly different pole polarities shown in FIG. 1 lb.

An advantage of the U-shaped cores is that they can be made as wide as the concentration zone (width 70') and all of the field produced by each core will be utilized. In the case of E-shaped cores, only the field connected with the center poles of the cores are utilized.

In all of the core structures described above an air gap of substantial size is employed. Such a substantial air gap is needed to provide the lossy" hysteresis characteristic when iron core structures are employed. The plate 16 may be made of a conductive nonmagnetic material to permit eddy currents to be developed in the plate. Such currents create magnetic fields which may enhance the magnetic concentratingaction.

Further, the eddy currents may enhance concentration when an electrically conductive material is being operated upon by the concentration by providing appropriate electrical fields.

In connection with the embodiment of the invention shown in FIG. 1, it has been found that E-shaped cores made of A.I.S.I. M 19 steel and wrapped with two windings as shown in FIG. 7a (turns ratio 1:1 and each rated at 25 amperes rms) are suitable for the concentration of ferromagnetic ore. Such core and coil structure was connected in a circuit as shown in FIG. 7b and was energized by standard line voltage (1 10 volts, 60 cycles per second). A diode having a 400 volt peak inverse voltage, a maximum reverse current at C. of 5 mil aniperes, a maximum voltage drop of 0.7 volts and a peak forward current of 300 amperes was employed in such a circuit. It has also been found that variation of resistance in the secondary circuit, such as represented by the resistor 54 in FIG. 6,-

has an effect upon the concentrating characteristics'of the apparatus. For example, the magnitude of the secondary winding current (FIG. 8a) will be changed by variation of the secondary resistance, thereby changing the net magnetizing force (FIG. 8b).

In connection with the explanation of the invention above, it should be understood that the waveform diagrams of FIGS. 311-311 and 8a-8a', which have been included to provide a basis for explaining the invention, are theoretically derived curves. It will also be understood that the theory of operation of the invention has been included to aid in an understanding of the invention. This theory, which represents the present understanding of the invention, should in no way limit the invention. It should be further noted that the representative embodiments' disclosed herein are susceptible of modification. Thus, the invention should be taken to be defined by the following claims.

We claim:

1. In a ferromagnetic ore concentrator, the combination comprising:

a. means defining an ore concentration zone;

b. means for introducing a particulate material into the zone, said material including ferromagnetic particles; and means for creating within the zone a magnetic field that exerts forces on the ferromagnetic particles and cyclically varies to and from substantially zero intensity and is of a single polarity and has a value greater than zero intensity throughout a major portion of each cycle of variation.

2. A ferromagnetic ore concentrator as defined in claim I, wherein the field creating means provides a magnetic field which alternates between opposing polarities.

3. A ferromagnetic ore concentrator as defined in claim 2, wherein the field creating means provides a field whose integral over time for one polarity substantially exceeds the integral over time for the opposing polarity during each cycle.

4. A ferromagnetic ore concentrator as defined in claim ll, wherein the field creating means includes primary coil means and secondary coil means magnetically coupled together.

5. A ferromagnetic ore concentrator as defined in claim 1, wherein said magnetic field is created by first means providing a magnetizing force of one polarity and of a substantially constant magnitude, and second means for providing a magnetizing force which alternates between substantially equal and opposite polarities.

6. A ferromagnetic ore concentrator as defined in claim 1, wherein the field creating means provides a magnetic field in which lines of force extend substantially in the direction of particle movement through the zone.

7. A ferromagnetic ore concentrator as defined in claim 6, wherein said concentration zone defining means includes an inclines inclined nonmagnetic plate, said introducing means introduces particulate material including ferromagnetic particles on one side of said plate at the upper portion thereof, and said magnetic field creating means is positioned on the other side of said inclined plate.

S. A ferromagnetic ore concentrator as defined in claim 7, including means for varying the inclination of one or more portions of said plate.

9. A ferromagnetic ore concentrator as defined in claim 7, wherein said field creating means comprises a plurality of magnetic core structures positioned one over another adjacent to the plate, each core structure including one or more coil means wrapped thereon, the polarity of adjacent ones of said coil means providing for alternation of magnetic poles along the plate at any instant oftime.

it A ferromagnetic ore concentrator as defined in claim 1, wherein said means defining said ore concentration zone per mits said particulate material to fall by gravity through said zone, and said magnetic field creating means provides a magnetic field having a component acting against the gravitational force.

11. A ferromagnetic ore concentrator as defined in claim 10. wherein said magnetic field creating means provides a magnetic field varying in direction at selected locations in said ore concentration zone.

12. in a ferromagnetic ore concentrator, the combination comprising:

a. means defining an ore concentration zone;

b. means for introducing a particulate material into the zone, said material including ferromagnetic particles; and means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and of a single polarity and a value greater than zero intensity throughout a major portion of each cycle of variation, wherein the field creating means includes primary coil means and secondary coil means magnetically coupled together, and wherein said primary coil means is energized by an alternating current supply, and including diode means connected in series with the secondary coil means for limiting the flow of current therethrough substantially to a single direction.

13. A ferromagnetic'ore concentrator as defined in claim 5, wherein said field creating means includes a magnetic core structure having one or more legs upon which the primary and secondary coil means are wrapped.

14. A ferromagnetic ore concentrator as defined in claim 7, wherein the magnetic core structure includes three legs, and in which the primary and secondary coil means are wrapped about a middle one of the legs.

15. A ferromagnetic ore concentrator as defined in claim 7, wherein the magnetic core structure has two legs and the primary and secondary coil means are wrapped upon one of the legs.

16. In a ferromagnetic ore concentrator, the combination comprising:

a, means defining an ore concentration zone;

b. means for introducing a particulate material into the zone, said material including ferromagnetic particles; and

c. means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and of a single polarity throughout a major portion of each cycle of variation, wherein the field creating means includes primary coil means and secondary coil means magnetically coupled together, said primary coil means is energized by an alternating current supply, and including diode means connected in series with the secondary coil means for limiting the flow of current therethrough substantially to a single direction, and including variable resistor means in series with said diode means.

17. In a ferromagnetic ore concentrator, the combination comprising:

a means defining an ore concentration zone;

b. means for introducing a particulate material into the zone, said material including ferromagnetic particles; and

c. means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and of a single polarity throughout a major portion iii of each cycle of variation, wherein the field creating means inc udes primary coil means and secondary COl means magnetically coupled together, said primary coil means is energized by an alternating current supply, and including diode means connected in series with the secondary coil means for limiting the flow of current therethrough substantially to a single direction, and said field creating means includes a magnetic core structure having two legs, and the primary and secondary coil means comprise a primary and a secondary coil concentrically wound about each one of the legs.

18. In a ferromagnetic ore concentrator, the combination comprising:

a. means defining an ore concentration zone;

b. means for introducing a particulate material into the zone, said field material including ferromagnetic particles; and

0. means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and of a single polarity throughout a major portion of each cycle of variation, wherein said field creating means includes a permanent magnet core structure having two legs, first and second coil means wound on different legs, and an alternating current supply for energizing the first and second coil means.

19. In a ferromagnetic ore concentrator, the combination comprising: i

a. means defining an ore concentration zone;

b. means for introducing a particulate material into the zone, said material including ferromagnetic particles; and

c. means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and ofa single polarity throughout a major portion of each cycle of variation, wherein said field creating means includes a magnetic core structure having two legs joined by a bridging member, first and second coil means wound on different legs of the core structure, an alternating current supply for energizing said first and second coil means, and third coil means wound on the bridging member of the core structure.

20. A ferromagnetic ore concentrator as defined in claim 19, wherein the third coil means is energized by a direct current supply.

21. A ferromagnetic ore concentrator as defined in claim 19, including diode means connected in series with the third coil means for limiting the flow of current through the third coil means substantially to a single direction.

22. A method of concentrating particles, at least some of which are ferromagnetic, comprising the steps of:

a. introducing the particles into a concentration zone by movement of the particles in a predetermined direction through an entrance to said zone;

b. concurrently subjecting all the particles in the zone to a first force transverse to said predetermined direction and tending to move all the particles out of the zone through a first exit; and

c. concurrently subjecting only the ferromagnetic particles in the zone to a second force acting in a direction dif ferent from that of the first force and tending to move only the ferromagnetic particles out of the zone through a second exit by application of a magnetic field cyclically varying to and from substantially zero intensity and of a single polarity and a value greater than zero intensity throughout a major portion of each cycle of variation.

23. A method as defined in claim 22, wherein said first force is the force of gravity, and said magnetic field includes a component acting against said gravitational force.

24. A method as defined in claim 23, wherein the direction of said magnetic field varies at selected locations in said ore concentration zone.

Patent No. 3,55 ,5

Dated 5 January lQLl John Ernest Burgener and Peter Mladenovich principles-;

Column 8, line should be deleted;

Column 9, line line line line .3 35, 39, &3,

(SEAL) Atteflt:

EDWARD M.F1'.ETCHER,JR. Attesting Officer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as show below:

after after after "the",

after "below." should be a new after "and", "the AC" should be deleted and substitute therefor --illustrate the magnetic beginning of the line, "inclines" beginning of the line, insert --c.--

Signed and sealed this 21st day of December 1971.

ROBERT GOT'I'SCHALK Acting Commissioner of Patent 

2. A ferromagnetic ore concentrator as defined in claim 1, wherein the field creating means provides a magnetic field which alternates between opposing polarities.
 3. A ferromagnetic ore concentrator as defined in claim 2, wherein the field creating means provides a field whose integral over time for one polarity substantially exceeds the integral over time for the opposing polarity during each cycle.
 4. A ferromagnetic ore concentrator as defined in claim 1, wherein the field creating means includes primary coil means and secondary coil means magnetically coupled together.
 5. A ferromagnetic ore concentrator as defined in claim 1, wherein said magnetic field is created by first means providing a magnetizing force of one polarity and of a substantially constant magnitude, and second means for providing a magnetizing force which alternates between substantially equal and opposite polarities.
 6. A ferromagnetic ore concentrator as defined in claim 1, wherein the field creating means provides a magnetic field in which lines of force extend substantially in the direction of particle movement through the zone.
 7. A ferromagnetic ore concentrator as defined in claim 6, wherein said concentration zone defining means includes an inclines inclined nonmagnetic plate, said introducing means introduces particulate material including ferromagnetic particles on one side of said plate at the upper portion thereof, and said magnetic field creating means is positioned on the other side of said inclined plate.
 8. A ferromagnetic ore concentrator as defined in claim 7, including means for varying the inclination of one or more portions of said plate.
 9. A ferromagnetic ore concentrator as defined in claim 7, wherein said field creating means comprises a plurality of magnetic core structures positioned one over another adjacent to the plate, each core structure including one or more coil means wrapped thereon, the polarity of adjacent ones of said coil means providing for alternation of magnetic poles along the plate at any instant of time.
 10. A ferromagnetic ore concentrator as defined in claim 1, wherein said means defining said ore concentration zone permits said particulate material to fall by gravity through said zone, and said magnetic field creating means provides a magnetic field having a component acting against the gravitational force.
 11. A ferromagnetic ore concentrator as defined in claim 10, wherein said magnetic field creating means provides a magnetic field varying in direction at selected locations in said ore concentration zone.
 12. In a ferromagnetic ore concentrator, the combination comprising: a. means defining an ore concentration zone; b. means for introducing a particulate material into the zone, said material including ferromagnetic particles; and means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and of a single polarity and a value greater than zero intensity throughout a major portion of each cycle of variation, wherein the field creating means includes primary coil means and secondary coil means magnetically coupled together, and wherein said primary coil means is energized by an alternating current supply, and including diode means connected in series with the secondary coil means for limiting the flow of current therethrough substantially to a single direction.
 13. A ferromagnetic ore concentrator as defined in claim 5, wherein said field creating means includes a magnetic core structure having one or more legs upon which the primary and secondary coil means are wrapped.
 14. A ferromagnetic ore concentrator as defined in claim 7, wherein the magnetic core structure includes three legs, and in which the primary and secondary coil means are wrapPed about a middle one of the legs.
 15. A ferromagnetic ore concentrator as defined in claim 7, wherein the magnetic core structure has two legs and the primary and secondary coil means are wrapped upon one of the legs.
 16. In a ferromagnetic ore concentrator, the combination comprising: a. means defining an ore concentration zone; b. means for introducing a particulate material into the zone, said material including ferromagnetic particles; and c. means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and of a single polarity throughout a major portion of each cycle of variation, wherein the field creating means includes primary coil means and secondary coil means magnetically coupled together, said primary coil means is energized by an alternating current supply, and including diode means connected in series with the secondary coil means for limiting the flow of current therethrough substantially to a single direction, and including variable resistor means in series with said diode means.
 17. In a ferromagnetic ore concentrator, the combination comprising: a. means defining an ore concentration zone; b. means for introducing a particulate material into the zone, said material including ferromagnetic particles; and c. means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and of a single polarity throughout a major portion of each cycle of variation, wherein the field creating means includes primary coil means and secondary coil means magnetically coupled together, said primary coil means is energized by an alternating current supply, and including diode means connected in series with the secondary coil means for limiting the flow of current therethrough substantially to a single direction, and said field creating means includes a magnetic core structure having two legs, and the primary and secondary coil means comprise a primary and a secondary coil concentrically wound about each one of the legs.
 18. In a ferromagnetic ore concentrator, the combination comprising: a. means defining an ore concentration zone; b. means for introducing a particulate material into the zone, said field material including ferromagnetic particles; and c. means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and of a single polarity throughout a major portion of each cycle of variation, wherein said field creating means includes a permanent magnet core structure having two legs, first and second coil means wound on different legs, and an alternating current supply for energizing the first and second coil means.
 19. In a ferromagnetic ore concentrator, the combination comprising: a. means defining an ore concentration zone; b. means for introducing a particulate material into the zone, said material including ferromagnetic particles; and c. means for creating a magnetic field within the zone, said field exerting forces on the ferromagnetic particles, said field cyclically varying to and from substantially zero intensity and of a single polarity throughout a major portion of each cycle of variation, wherein said field creating means includes a magnetic core structure having two legs joined by a bridging member, first and second coil means wound on different legs of the core structure, an alternating current supply for energizing said first and second coil means, and third coil means wound on the bridging member of the core structure.
 20. A ferromagnetic ore concentrator as defined in claim 19, wherein the third coil means is energized by a direct current supply.
 21. A ferromagnetic ore concentrator as defined in claim 19, including diOde means connected in series with the third coil means for limiting the flow of current through the third coil means substantially to a single direction.
 22. A method of concentrating particles, at least some of which are ferromagnetic, comprising the steps of: a. introducing the particles into a concentration zone by movement of the particles in a predetermined direction through an entrance to said zone; b. concurrently subjecting all the particles in the zone to a first force transverse to said predetermined direction and tending to move all the particles out of the zone through a first exit; and c. concurrently subjecting only the ferromagnetic particles in the zone to a second force acting in a direction different from that of the first force and tending to move only the ferromagnetic particles out of the zone through a second exit by application of a magnetic field cyclically varying to and from substantially zero intensity and of a single polarity and a value greater than zero intensity throughout a major portion of each cycle of variation.
 23. A method as defined in claim 22, wherein said first force is the force of gravity, and said magnetic field includes a component acting against said gravitational force.
 24. A method as defined in claim 23, wherein the direction of said magnetic field varies at selected locations in said ore concentration zone. 